The present invention relates to a developing apparatus that is used, for example, in an electrophotographic color image forming apparatus.
In recent years, the use of color images has become common in offices, and more and more electrophotographic color image forming apparatuses are commercially available. Color printers and color MFPs, in particular, are in wide use, and they have been improved in printing speed.
Unlike the conventional color copying machines, these types of apparatus are not maintained regularly. In other words, the maintenance by the user is required, and the user replaces the developing unit or toner unit with a new one. A conventional low-speed color image forming apparatus employs a one-component nonmagnetic type color developing unit so as to enable maintenance by the user.
If such a one-component nonmagnetic type color developing unit is applied to a high-speed color printer without any modifications, toner may adhere to a developing roller or a layer regulation blade, resulting in defective images.
This phenomenon holds true for a black-and-white printer or MFP as well. If a high-speed printer apparatus employs a one-component nonmagnetic developing unit, toner may adhere to a developing roller or a layer regulation blade, resulting in defective images.
The present invention has been made in consideration of the above circumstances, and the object of the invention is to provide a developing apparatus which can employ a high-speed one-component nonmagnetic type unit without adhesion of a developing agent to a developing roller and a layer regulation means, and which therefore enables production of images with reliable quality.
A developing apparatus of the present invention comprises: a developing roller for supplying a developing agent to an image carrier by rotation; a layer regulation member for regulating a layer thickness of the developing agent supplied to the developing roller; temperature sensing means for sensing a temperature of either the developing roller or the layer regulation member; and control means for controlling the rotation of the developing roller in accordance with a temperature sensed by the sensing means.
Another developing apparatus of the present invention comprises: a developing roller for supplying a developing agent to an image carrier by rotation; a layer regulation member for regulating a layer thickness of the developing agent supplied to the developing roller; temperature sensing means for sensing a temperature of either the developing roller or the layer regulation member; cooling means for cooling the developing roller by supplying air to the developing roller; and control means for controlling the air supply by the cooling means in accordance with a temperature sensed by the sensing means.
A further developing apparatus of the present invention comprises: first and second developing means which are selectively used and each of which includes a developing roller for supplying a developing agent to an image carrier by rotation, a layer regulation member for regulating a layer thickness of the developing agent supplied to the developing roller, and temperature sensing means for sensing a temperature of either the developing roller or the layer regulation member; and switching means, operating when one of the first and second developing means is in use, for switching the developing means in use to the developing means in accordance with a temperature sensed by the sensing means.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.